Vulnerability · Published Jun 22, 2026 · Assigned by Mattermost
CVE-2026-6673Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install
Medium 6.4
In plain English
A medium-severity missing authentication in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt the Jira integration via POST to /ac/installed during the pending-install window.. Mattermost Advisory ID: MMSA-2026-00654
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 11.7.1 | GHSA-jqgv-39mg-7c2r |
| Go | github.com/mattermost/mattermost-server | 11.6.3 | GHSA-jqgv-39mg-7c2r |
| Go | github.com/mattermost/mattermost-server | 11.5.6 | GHSA-jqgv-39mg-7c2r |
| Go | github.com/mattermost/mattermost-server | 10.11.18 | GHSA-jqgv-39mg-7c2r |
| Go | github.com/mattermost/mattermost-server | 10.11.18+incompatible, 11.5.6+incompatible, 11.6.3+incompatible, 11.7.1+incompatible | GO-2026-6483 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.7.0 – through 11.7.011.6.0 – through 11.6.211.5.0 – through 11.5.510.11.0 – through 10.11.17 |
Weakness: CWE-306 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H
References
- MMSA-2026-00654 vendor-advisory